The invention relates to a system comprising at least one encoder for coding a digital signal and at least one decoder for decoding a coded digital signal, which encoder is provided with
an input for receiving the digital signal, PA0 first data processing means, coupled to the input, for generating a first coded digital signal, PA0 first encoder feedback means for feeding back at least a section of the first data processing means, which first encoder feedback means comprise first encoder memory means, PA0 reduction means, coupled to the input, for reducing the received digital signal, PA0 second data processing means, coupled to the reduction means, for generating a second coded digital signal, PA0 second encoder feedback means for feeding back at least a section of the second data processing means, which second encoder feedback means comprise second encoder memory means, and PA0 encoder coupling means for coupling the second encoder feedback means to the first encoder feedback means, which encoder coupling means comprise encoder prediction means, PA0 first data reprocessing means for processing a first coded digital signal, PA0 first decoder memory means which are coupled to the first data reprocessing means, PA0 second data reprocessing means for processing a second coded digital signal, PA0 second decoder memory means which are coupled to the second data reprocessing means, and PA0 decoder coupling means for coupling the second decoder memory means to the first decoder memory means, which decoder coupling means comprise decoder prediction means. PA0 for deriving a position code from the digital signal, PA0 for comparing the position code with at least one adjustable code, and PA0 for decoupling, subject to a comparison result, the second encoder feedback means and the first encoder feedback means. PA0 for deriving the position code from a coded digital signal and for receiving the adjustable code, PA0 for comparing the position code with the adjustable code, and PA0 for decoupling, subject to a comparison result, the second decoder memory means and the first decoder memory means. PA0 an input for receiving the digital signal, PA0 first data processing means, coupled to the input, for generating a first coded digital signal, PA0 first encoder feedback means for feeding back at least a section of the first data processing means, which first encoder feedback means comprise first encoder memory means, PA0 reduction means, coupled to the input, for reducing the received digital signal, PA0 second data processing means, coupled to the reduction means, for generating a second coded digital signal, PA0 second encoder feedback means for feeding back at least a section of the second data processing means, which second encoder feedback means comprise second encoder memory means, and PA0 encoder coupling means for coupling the second encoder feedback means to the first encoder feedback means, which encoder coupling means comprise encoder prediction means, PA0 for deriving a position code from the digital signal, PA0 for comparing the position code with at least one adjustable code, and PA0 for decoupling, subject to a comparison result, the second encoder feedback means and the first encoder feedback means. PA0 first data reprocessing means for processing a first coded digital signal, PA0 first decoder memory means which are coupled to the first data reprocessing means, PA0 second data reprocessing means for processing a second coded digital signal, PA0 second decoder memory means which are coupled to the second data reprocessing means, and PA0 decoder coupling means for coupling the second decoder memory means to the first decoder memory means, which decoder coupling means comprise decoder prediction means. PA0 for deriving the position code from a coded digital signal and for receiving the adjustable code, PA0 for comparing the position code with the adjustable code, and PA0 for decoupling, subject to a comparison result, the second decoder memory means and the first decoder memory means. PA0 "Coded representation of picture and audio information", "TMI Compatibility Experiments", by I. Parke, ISO-IEC/JTC1/SC29/WG11, MPEG92/291
and which decoder is provided with
Such a system is known from "Coded representation of picture and audio information", "TMI Compatibility Experiments", by I. Parke, ISO-IEC/JTC1/SC29/WG11, MPEG92/291, in particular FIG. 1 (the encoder) and FIG. 2 (the decoder) thereof. The encoder based on layered coding comprises the input for receiving the digital signal to be coded, such as, for example, a television signal made up of picture elements (pixels or pels), and the first data processing means, coupled to the input, for generating the first coded digital signal (indicated by "T", "Q" in the abovementioned FIG. 1). The encoder furthermore comprises the first encoder feedback means for feeding back at least a section of the first data processing means in order to make the coding proceed more efficiently. The first encoder feedback means comprise the encoder memory means, and first encoder movement prediction means (indicated as a whole by "Mc" in the abovementioned FIG. 1) which may be situated in series therewith. The encoder also comprises the reduction means, coupled to the input, for reducing the received digital signal, the second data processing means, coupled to the reduction means, for generating a second coded digital signal, and the second encoder feedback means for feeding back at least a section of the second data processing means in order to make the coding proceed more efficiently. The second encoder feedback means comprise the second encoder memory means and second encoder movement prediction means, which may be situated in series therewith, and are coupled, via the encoder coupling means, to the first encoder feedback means (the reduction means, second data processing means and second encoder primary means are not shown directly in the abovementioned FIG. 1 but are evident therefrom, in a manner known to the person skilled in the art, because they are indicated symbolically by "MPEG-1"). The encoder coupling means comprise the encoder prediction means (indicated by "Uc" in the abovementioned FIG. 1).
Such a system, provided with first and second data processing means, is, as it were, made up of two layers: the first data processing means generate the first coded digital signal, which has the highest resolution because said signal is obtained by processing the received digital signal, and the second data processing means generate the second coded digital signal, which has the lowest resolution because said signal is obtained by processing the received digital signal reduced by the reduction means. The two signals are then transmitted by means of multiplexing and demultiplexing to the decoder, which is based on layered decoding and which, in the case of coding on the basis of high resolution, uses both signals and, in the case of decoding on the basis of low resolution, uses only the second coded digital signal. The decoder comprises the first data reprocessing means for processing a first coded digital signal (indicated by, respectively, "Q.sup.-1 ", "T.sup.-1 " and by "MPEG-2 bits" in the abovementioned FIG. 2), the first decoder memory means (and decoder movement compensation means which may be situated in series therewith, indicated as a whole by "Mc" in the abovementioned FIG. 2), which are coupled to the first data reprocessing means, the second data reprocessing means for processing a second coded digital signal (indicated by, respectively, "Q.sup.-1 ", "T.sup.-1 " and by "MPEG-1 bits" in the abovementioned FIG. 2), and the second decoder memory means (and second decoder movement compensation means which may be situated in series therewith, indicated as a whole by "Mc" in the abovementioned FIG. 2) which are coupled to the second data reprocessing means and, via the decoder coupling means, to the first decoder memory means. The decoder coupling means comprise the decoder prediction means (indicated by "Uc" in the abovementioned FIG. 2).
The known system has the disadvantage that it exhibits a certain inefficiency in coding and decoding if the layer which codes with high resolution codes a signal which corresponds, for example, to an HDTV picture and the layer which codes with low resolution codes a signal corresponding to a conventional tv picture derived from the HDTV picture.